A loss of resolution was experimentally observed when using a 40-mm microchannel plate image-intensifier tube at high gains. A controlled set of experiments was performed to study this effect. A resolution chart, under constant illumination, was viewed while a lens-image intensifier combination was varied so as to maintain constant light output from the system. Significant resolution degradation can occur at the higher gains. Experiments were performed to determine whether this phenomenon was due to photon statistics at the photocathode or to an increase in noise at the higher microchannel plate (MCP) voltages. The experiments showed that the controlling factor was the voltage across the MCP and not the photon statistics. A theoretical calculation is presented that confirms and augments the experimental results.